Management of the Diabetic Foot: Preventing Amputation

Marvin E. Levin, MD

Disclosures

South Med J. 2002;95(1) 

In This Article

Peripheral Neuropathy

Peripheral neuropathy with loss of sensation is the major cause of diabetic foot ulcers and amputation. Although the exact etiology of PN is unknown, it is probably the result of a combination of metabolic events, including the accumulation of glucose, sorbitol, and fructose in the nerve; a decrease in myo-inositol, which is important for nerve conduction; and ischemia due to narrowing of the vessels in the vasa nervorum.

Patients with diabetes should undergo examination of the peripheral nerves at least once a year. Loss of the Achilles tendon reflex and vibratory sensation are the earliest symptoms of PN. Although these symptoms usually occur together, they can occur independently.

The most important neurologic finding in PN is the loss of protective sensation.[9,10] The use of a pinprick to assess sensation is outdated. Sensation assessments are now carried out using the Semmes-Weinstein 5.07 monofilament. This simple device is pressed against the skin until it buckles; the amount of pressure is equal to 10 grams of linear strength. Inability to perceive pressure at this level indicates severe PN and puts the patient at high risk for the development of foot ulcers. This is a simple test that the patient can do at home,[9,10,11] and it is currently believed to be the most practical method of risk assessment for PN.[9,10]

Foot Problems
Causative factors include:
  • Neuropathy

  • Ischemia

  • Infection

The effectiveness of tight blood glucose control was shown in the Diabetes Control and Complications Trial.[11] To date, it is the only means of preventing neuropathy or slowing its progression.

Foot deformities are notoriously common in the diabetic patient with PN. Patients with diabetes are prone to having cocked-up toes, hammer toes, and/or claw toes. These deformities are frequently associated with thinning or shifting of the fat pad under the metatarsal heads. The areas at the top of the toes, the tips of the toes, and under the metatarsal heads are therefore vulnerable to ulceration, infection, and, subsequently, osteomyelitis, gangrene, and amputation. The ideal treatment is prophylactic surgery to straighten the toes while circulation is good. When surgery is not possible, the patient should wear a shoe with a large toe-box to accommodate the cocked-up toes and/or an in-depth shoe with a cushioned insole to reduce the pressure over the metatarsal heads and the tips of the toes. This will decrease the probability of ulceration in those areas.

Chance Of Amputation of Opposite Leg After First Amputation
1-3 years 3-5 years
42% 56%

Charcot's foot is the classic diabetic foot deformity. Patients with this deformity frequently present with bounding pulses in a swollen, red, warm foot. The patient often gives a history of having sustained a sprain or minor injury to the ankle or foot a few days to a week before the development of swelling and erythema of the foot. These signs represent the acute onset of the Charcot foot. Despite these changes in the foot, there is only minimal discomfort. At this acute stage, the presence of cellulitis must be ruled out. Radiographs taken at this time usually reveal no abnormalities. The classic history of minor trauma, the absence of any portal of entry for infection, and the absence of other clinical signs or laboratory findings of infection are highly suggestive that the patient has an acute Charcot's foot, however.

The patient should be placed on non-weight-bearing status as soon as Charcot's foot is diagnosed. If the patient continues to walk, a variety of fractures will occur within a period of several weeks to months, particularly at the tarsometatarsal joint; fragmentation and dissolution of the bone are likely sequelae. If the patient is not casted and placed on non-weight-bearing status, the ankle joint will collapse, and the foot will take on a club-foot-like appearance and a rocker-bottom configuration. If the patient continues to walk without protection of the foot with a cast or special footwear, ulceration will occur on the mid-plantar surface of the foot. In some cases, surgical procedures can be performed to correct the deformity and/or stabilize the foot or joint. The deformed foot requires the use of a specially molded therapeutic shoe.[12,13,14]

Wound Debridement Modern Approach
  • Radical, aggressive debridement is mandatory

  • Goal -- > Healthy, noninfected, bleeding tissue

Failure to recognize the acute stage of Charcot's foot is not uncommon. These patients frequently are treated for months with a variety of antibiotics until finally the foot collapses. At that time, the correct diagnosis is made, usually as a result of x-rays. The end result is a foot that is vulnerable to ulceration. Failure to diagnose the Charcot's foot in a timely fashion frequently leads to a malpractice suit for substandard care.

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